Compact Camcorders Gain on Big Boys : Sales are up for VHS-C and 8mm units. They are costlier but more portable than full-size VHS models.

Camcorder sales rose 33.7% to 1.9 million in the first nine months of 1990, and industry estimates are that the figure will have climbed to nearly 3 million by the end of the year. Generally priced in the $700-$1,000 range, they are a popular big-ticket Christmas gift.

The most popular camcorder (a portable unit that combines a video camera and a VCR) is the full-size VHS unit, which uses a standard blank videotape and generally weighs from five to eight pounds. It controls half the lucrative market.

But the compacts (VHS-C and 8mm)--which weigh from two to four pounds and use mini-cassettes--really whittled away at the market share of the full-size unit last summer.

According to a survey printed in Twice, a consumer electronics trade journal, 51% of the camcorders sold between May and August were compacts, with VHS-C leading the surge. VHS-C is a compact version of VHS, with the VHS-C cassette playable in a standard VCR with an adapter.

The 8mm format, which is dominated by Sony, features the smallest and lightest camcorders.

If you plan to buy a camcorder, here are several points to consider:

* Needs. Pinpoint your primary uses for the unit. For normal purposes--weddings, birthday parties, kids’ soccer games--the full-size VHS unit will do. Many have no fancy features, but most people don’t need them. The main reason this unit accounts for half the market is price: It can be found discounted under $700, several hundred dollars cheaper than most compacts. Another plus is the fact that the full-size unit uses standard blank tapes, which are readily playable in any VCR and are cheaper than the compact blank tapes.

If you plan to use the unit when traveling, however, you should think about a compact, which is lighter. One reason compact sales were up last summer was that people were buying them to take on vacation.

* Features: These add to the price, but are desirable in some cases. If you want nicely edited tapes, then buy a camcorder with a flying erase head, which allows for cuts from scene to scene without visual noise. And with a fade button you can fade out of a scene like the pros. If you want the best special effects, you’ll have to spend at least $2,000 for a machine that offers digital capabilities.

* Jitters: Camcorder pictures are generally shaky since it’s hard to hold the units perfectly still. You’ll generally get steadier pictures with the full-size units. The Panasonic PV-40, a new, elite VHS-C “palmcorder,” has special circuitry that automatically steadies the picture, called electronic image stabilization (EIS). PV-40, the only unit on the market with this feature, retails for $1,400.

* Tape: You get more tape time with the full-size VHS and the 8mm--two hours at the fastest speed--which offer the best-quality picture. With the VHS-C, you get only half an hour at the fastest speed. Also, remember that compact tapes are getting easier to find all the time, but you may have trouble finding them in small towns and out-of-the-way places.

* Light limits: Don’t expect camcorders to perform well in poorly lit situations. Look at the lux number when you’re buying a camcorder. The lower the lux number, supposedly the better it operates in dim light. But in dim light you get only a passable picture, despite manufacturer claims.

* Sound limits: The built-in mikes on camcorders are notoriously bad. If you need excellent sound, invest in a microphone.